A device to recover heat from waste water coming out of a basin is known from the prior art, in particular from the document WO 2011/138467. This device according to the prior art recovers heat from waste water coming out of a basin, for example a shower basin, using a plate heat exchanger. Such a device has high thermal efficiency, however, in certain circumstances, in particular when the exchanger of this device must be installed in a confined and difficult to access place, these installation conditions do not allow an operation of the device in optimal conditions. Thus, when the exchanger is permanently installed in a false ceiling or in an interjoist, especially when, for space requirements, it is placed horizontally, said exchanger acts as a siphon, and an air bubble forms in the top of the exchanger, which air bubble reduces the useful heat exchange area and therefore the efficiency of the heat recovery device, while concentrating fouling in a small volume of the exchanger.